The present invention relates generally to video image enhancement systems, and, more particularly, to hardware convolvers for processing of real-time digitized video images.
The use of local operators such as the 3.times.3 convolution mask operator for two-dimensional image filtering is a well developed art known to be quite effective for edges, contour enhancement, and detection. In the article by Guner S. Robinson, entitled "Edge Detection by Compass Gradient Masks", published in the COMPUTER GRAPHICS AND IMAGE PROCESSING, Vol. 6, pp. 492-501, 1977, Robinson presented more than thirty (30) 3.times.3 convolution masks. Such operator is most popular for enhancement of contour--one of the most important features of an image. With an appropriate mask, a neighborhood averaging for noise reduction (low-pass) can also be achieved.
Since such operators are relatively simple, a number of hardware implementations have been built and proposed. In an article entitled "Chip Helps Detect Target Automatically", published in ELECTRONICS, pp. 41, March, 1978, as well as an article by Joseph E. Hall and James D. Aurtney, entitled "Real-Time Image Enhancement Using 3.times.3 Pixel Neighborhood Operator Functions", published in OPTICAL ENGINEERING, Vol. 19, No. 3, pp. 241, May, 1980, an analog system is presented utilizing a charge coupled device (CCD) to generate the one line delay required, and to perform the convolution operation as well. Such systems are currently limited by the CCD transfer rate (2 MHz). In an article by R. Eskenazi and J. M. Wild, entitled "Low-Level Processing for Real-Time Image Analysis", in the September, 1979 JPL Publication, and in an article by P. Wambacq et al, entitled "Description of Two Hardware Convolvers As A Part Of A General Image Computer", published in the Proceedings of PR & IP, pp. 294, August, 1981, digitally-implemented operators are proposed. The first one describes a fixed pipeline convolution unit while the second utilizes nine (9) expensive digital multipliers and summation networks. These prior art systems are rather complex and are considered to be inefficient in terms of cost, size and power consumption or are limited by the transfer rate of system processing.
It is accordingly a primary object of the present invention to provide an improved video image enhancement apparatus which is efficient and capable of high transfer rates.